A device of this type, i.e., a device for controlling an opening cross section in a combustion cylinder, is disclosed in published German Patent Application No. 198 26 047. This device has a double-acting hydraulic working cylinder as the actuator, i.e., valve actuator; an actuating piston which is axially displaceably guided in this working cylinder is fixedly connected to the valve shaft of the gas exchange valve that is integrated into the combustion cylinder or it forms the end thereof, which is remote from the valve closure member. With its two end faces which face away from one another, the actuating piston delimits a first and second pressure chamber in the working cylinder. While the first pressure chamber through which a piston displacement in the direction of valve closing is induced is constantly acted upon by fluid under pressure, the second pressure chamber through which a piston displacement is induced in the direction of valve opening is acted upon with fluid under pressure in a controlled manner with the help of control valves, preferably 2/2-way solenoid valves, or the pressure is relieved to approximately ambient pressure. The fluid under pressure is supplied by a regulated pressure supply. A first control valve connects the second pressure chamber to the pressure supply and a second control valve connects the second pressure chamber to a relief line opening into a fluid reservoir. In the closed state of the gas exchange valve, the second pressure chamber is separated from the pressure supply by the first control valve, which is closed, and is connected to the relief line through the second control valve, which is opened, so that the actuating piston is displaced into its closed position by the fluid pressure prevailing in the first pressure chamber. For opening the gas exchange valve, the control valves are switched over, so that the second pressure chamber is cut off from the relief line and is connected to the pressure supply. The gas exchange valve opens because the piston face of the actuating piston is larger in the second pressure chamber than the effective area of the actuating piston in the first pressure chamber, the length of the opening stroke depending on the formation of the electric control signal applied to the first control valve, and the opening speed depends on the fluid pressure, which is controlled by the pressure supply. To close the gas exchange valve, the control valves are switched over again, whereby the second pressure chamber, which is cut off from the pressure supply, is connected to the relief line, and the fluid pressure prevailing in the first pressure chamber returns the actuating piston to its valve closure position, so that the gas exchange valve is closed by the actuating piston.
With a device such as the one described above, there is a need for rapid closing of the gas exchange valve, and at the same time, a low impact velocity of the valve closure member on the valve seat, which must not exceed certain limit values for reasons of noise level and wear.